One challenge of measuring color off or through a sample under test is the spatial inhomogeneity of the color of the sample. In other words, the color may vary somewhat over the sample. The inhomogeneity may be caused by fabrication error of the sample, inherent asymmetry of the sample, such as weave of paper on which the sample is formed or surface structure on the sample, as well as bending or distortion of the sample. As any one or many situations can occur in a color sample, measuring devices may provide inaccurate measurements of the color.
The effects of test sample inhomogeneity may become even more problematic when used with spatial arrays, where sensing may be spread out spatially. Each sensor may be provided color from different portions of the sample, which may or may not be the same, leading to measurement errors.
Prior color measuring approaches have included taking multiple measurements of the same sample in different positions, and then averaging them together. This approach brings uncertainty and additional errors into play, and further takes more time to measure and average properly. In other approaches, some kind of light pipe may be used to spatially scramble light reflected off or through the sample. The degree to which the scrambling or mixing can occur may depend on a spot size at the end of the pipe, the length of the pipe in relation to size, and input light distribution coming into the light pipe to be scrambled. If a large sample is desired, then the pipe is long, which may not fit well with cost and space constraints for a particular measurement device.